This invention relates to internal combustion engines of the type having a throttle controlling airflow to a combustion chamber, fuel supply apparatus for forming a combustible charge in the combustion chamber and EGR apparatus for introducing recirculated exhaust gasses to the fuel charge to control the dilution thereof. In particular, it relates to such engines in which the rapid closing of the throttle, in a throttle tipout condition, produces increasing intake manifold vacuum and thus causes an unscheduled temporary increase in dilution. This may occur with a separately controlled EGR valve or with internal EGR control using a variable valve lift apparatus for combustion chamber exhaust valve control.